Many medical device applications require advancement of device in a reduced profile to a remote site within the body, where on reaching a target site the device assumes or is deployed into a relatively larger profile. Applications in the cerebral vasculature are one such example of medical procedures where a catheter advances from a remote part of the body (typically a leg) through the vasculature and into the cerebral region of the vasculature to deploy a device. Accordingly, the deployed devices must be capable of achieving a larger profile while being able to fit within a small catheter or microcatheter. In addition, the degree to which a physician is limited in accessing remote regions of the cerebral vasculature is directly related to the limited ability of the device to constrain into a reduced profile for delivery.
Treatment of ischemic stroke is one such area where a need remains to deliver a device in a reduced profile and deploy the device to ultimately remove a blockage in an artery leading to the brain. Left untreated, the blockage causes a lack of supply of oxygen and nutrients to the brain tissue. The brain relies on its arteries to supply oxygenated blood from the heart and lungs. The blood returning from the brain carries carbon dioxide and cellular waste. Blockages that interfere with this supply eventually cause the brain tissue to stop functioning. If the disruption in supply occurs for a sufficient amount of time, the continued lack of nutrients and oxygen causes irreversible cell death (infarction). Accordingly, immediate medical treatment of an ischemic stroke is critical for the recovery of a patient.
Naturally, areas outside of ischemic stroke applications can also benefit from improved devices. Such improved devices can assume a profile for ultimate delivery to remote regions of the body and can remove obstructions. There also remains a need for devices and systems that can safely remove the obstruction from the body once they are secured within the device at the target site. Furthermore, there remains a need for such devices that are able to safely removed once deployed distally to the obstructions in the even that the obstructions is unable to be retrieved.
Furthermore, the techniques for treating strokes described herein can be combined with stenting as well as the delivery of clot dissolving substances.
The use of stents to treat ischemic stroke is becoming more common. Typically, a physician places an unexpanded stent across a clot and then expands the stent to compress the clot and partially open the vessel. Once the vessel is at least partially open, clot dissolving fluids, such as t-PA or urokinase, can be deployed through a microcatheter to further dissolve the clot. However, these fluids generally take a long time to dissolve clot (sometimes up to several hours). Thus, the use of these fluids has not been terribly effective at dissolving clot in vessels where a complete blockage occurs. The use of a stent allows immediate flow to the vessel, the fluid can then be administered over several hours to dissolve the clot. Once the clot dissolves, the stem can either be left in place (i.e., a permanent stent), or removed (i.e., a temporary stent).
However, once blood flow is restored, a portion of the clot dissolving substance is dispersed downstream of the clot via blood flow. This minimizes the contact time and amount between the fluid and the clot thereby decreasing the efficiency of the stent and fluid treatment.
The methods, devices and systems, address the problems described above.